Read/Write Base Station U2270B

Transcription

1 Features Carrier Frequency f osc 100 khz to 150 khz Typical Data Rate up to 5 kbaud at 125 khz Suitable for Manchester and Bi-phase Modulation Power Supply from the Car Battery or from 5- Regulated oltage Optimized for Car Immobilizer Applications Tuning Capability Microcontroller-compatible Interface Low Power Consumption in Standby Mode Power-supply Output for Microcontroller Applications Car Immobilizers Animal Identification Access Control Process Control Read/Write Base Station 1. Description The is an IC for IDIC read/write base stations in contactless identification and immobilizer systems. The IC incorporates the energy-transfer circuit to supply the transponder. It consists of an on-chip power supply, an oscillator and a coil driver optimized for automotive-specific distances. It also includes all signal-processing circuits which are necessary to transform the small input signal into a microcontroller-compatible signal. Figure 1-1. System Block Diagram Transponder/TAG Read/write base station Transponder IC RF field typ. 125 khz Osc NF read channel Carrier enable Data output MCU Unlock System Rev.

2 Figure 1-2. Block Diagram D S EXT S Batt Standby Power supply COIL1 = 1 MS CFE COIL2 Driver & Oscillator Frequency adjustment RF DGND Amplifier Output Input & Lowpass filter Schmitt trigger HIPASS GND OE 2

3 2. Pin Configuration Figure 2-1. Pinning GND OUTPUT OE INPUT MS CFE DGND COIL HIPASS RF S STANDBY BATT DS EXT COIL1 Table 2-1. Pin Description Pin Symbol Function 1 GND Ground 2 OUTPUT Data output 3 OE Data output enable 4 INPUT Data input 5 MS Mode select coil 1: common mode/differential mode 6 CFE Carrier frequency enable 7 DGND Driver ground 8 COIL2 Coil driver 2 9 COIL1 Coil driver 1 10 EXT External power supply 11 DS Driver supply voltage 12 Batt Battery voltage 13 STANDBY Standby input 14 S Internal power supply (5) 15 RF Frequency adjustment 16 HIPASS DC decoupling 3

4 3. Functional Description 3.1 Power Supply (PS) Figure 3-1. Equivalent Circuit of Power Supply and Antenna Driver D S EXT S Batt Standby internal supply 9 25 kω PS 12 kω COILx DR DGND The can be operated with one external supply voltage or with two externally-stabilized supply voltages for an extended driver output voltage or from the 12- battery voltage of a vehicle. The 12- supply capability is achieved via the on-chip power supply (see Figure 3-1). The power supply provides two different output voltages, S and EXT. S is the internal power supply voltage except for the driver circuit. Pin S is used to connect a block capacitor. S can be switched off by Standby pin. In standby mode, the chip s power consumption is very low. EXT is the supply voltage of the antenna s pre-driver. This voltage can also be used to operate external circuits, like a microcontroller. In conjunction with an external NPN transistor it also establishes the supply voltage of the antenna coil driver, DS. 4

5 3.2 Operation Modes to Power the The following section explains the 3 different operation modes to power the One-rail Operation All internal circuits are operated from one 5- power rail (see Figure 3-2). In this case, S, EXT and D S serve as inputs. Batt is not used but should also be connected to that supply rail. Figure 3-2. One Rail Operation Supply +5 (stabilized) D S EXT S Batt Standby Two-rail Operation In this application, the driver voltage, D S, and the pre-driver supply, EXT, are operated at a higher voltage than the rest of the circuitry to obtain a higher driver-output swing and thus a higher magnetic field (see Figure 3-3). S is connected to a 5- supply, whereas the driver voltages can be as high as 8. This operation mode is intended to be used in situations where an extended communication distance is required. Figure 3-3. Two Rail Operation Supply 7 to 8 (stabilized) 5 (stabilized) D S EXT S Batt Standby Battery-voltage Operation Using this operation mode, S and EXT are generated by the internal power supply (see Figure 3-4). For this mode, an external voltage regulator is not needed. The IC can be switched off via the Standby pin. EXT supplies the base of an external NPN transistor and external circuits, like a microcontroller (even in Standby mode). Pin EXT and Batt are overvoltage protected via internal Zener diodes (see Figure 3-1 on page 4).The maximum current into the pins is determined by the maximum power dissipation and the maximum junction temperature of the IC. 5

6 Figure 3-4. Battery Operation 7 to 16 D S EXT S Batt Standby Table 3-1. Characteristics of the arious Operation Modes Operation Mode External Components Required Supply-voltage Range One-rail operation Two-rail operation Battery-voltage operation 1 oltage regulator 1 Capacitor 2 oltage regulators 2 Capacitors 1 Transistor 2 Capacitors Optional for load dump protection: 1 Resistor 1 Capacitor Driver Output oltage Swing Standby Mode Available 5 ±10% 4 No 5 ±10% 7 to 8 6 to Oscillator (Osc) The frequency of the on-chip oscillator is controlled by a current fed into the R F input. An integrated compensation circuit ensures a wide temperature range and a supply-voltageindependent frequency which is selected by a fixed resistor between R F (pin 15) and S (pin 14). For 125 khz, a resistor value of 110 kω is defined. For other frequencies, use the following formula: R t [ kω] = f 0 [ khz] No 6 to 16 4 Yes This input can be used to adjust the frequency close to the resonance of the antenna. For more details refer to the section Applications on page 10 and to the application note ANT019. Figure 3-5. Equivalent Circuit of Pin R F S 2 kω R f R F 6

7 3.4 Filter (LPF) The fully-integrated lowpass filter (4th-order butterworth) removes the remaining carrier signal and high-frequency disturbances after demodulation. The upper cut-off frequency of the LPF depends on the selected oscillator frequency. The typical value is f Osc /18. That means that data rates up to f Osc /25 are possible if Bi-phase or Manchester encoding is used. A highpass characteristic results from the capacitive coupling at the input pin 4 as shown in Figure 3-6. The input voltage swing is limited to 2 pp. For frequency response calculation, the impedances of the signal source and LPF input (typical 220 kω) have to be considered. The recommended values of the input capacitor for selected data rates are given in the section Applications. Note: After switching on the carrier, the DC voltage of the coupling capacitor changes rapidly. When the antenna voltage is stable, the LPF needs approximately 2 ms to recover full sensitivity. Figure 3-6. Equivalent Circuit of Pin Input Bias R S Input 10 kω C IN 210 kω Bias Bias 3.5 Amplifier (AMP) The differential amplifier has a fixed gain, typically 30. The HIPASS pin is used for dc decoupling. The lower cut-off frequency of the decoupling circuit can be calculated as follows: f 1 cut = π C HP R i The value of the internal resistor R i can be assumed to be 2.5 kω. Recommended values of C HP for selected data rates can be found in the section Applications on page 10. 7

8 Figure 3-7. Equivalent Circuit of Pin HIPASS R + LPF R - Schmitt trigger Ref R R R i HIPASS C HP 3.6 Schmitt Trigger The signal is processed by a Schmitt trigger to suppress possible noise and to make the signal microcontroller compatible. The hysteresis level is 100 m symmetrically to the DC operation point. The open-collector output is enabled by a low level at OE (pin 3). Figure 3-8. Equivalent Circuit of Pin OE 7 µa OE 8

9 3.7 Driver (DR) The driver supplies the antenna coil with the appropriate energy. The circuit consists of two independent output stages. These output stages can be operated in two different modes. In common mode, the outputs of the stages are in phase. In this mode, the outputs can be interconnected to achieve a high-current output capability. Using the differential mode, the output voltages are in anti-phase. Thus, the antenna coil is driven with a higher voltage. For a specific magnetic field, the antenna coil impedance is higher for the differential mode. As a higher coil impedance results in a better system sensitivity, the differential mode should be preferred. The CFE input is intended to be used for writing data into a read/write or a crypto transponder. This is achieved by interrupting the RF field with short gaps. The various functions are controlled by the inputs MS and CFE (refer to the function table). The equivalent circuit of the driver is shown in Figure 3-1 on page 4. Figure 3-9. Equivalent Circuit of Pin MS 30 µa MS Figure Equivalent Circuit of Pin CFE 30 µa CFE 9

10 3.8 Function Table CFE MS COIL1 COIL2 Low Low High High Low High Low High High High Low High OE Output Standby Low Enabled Low Standby mode High Disabled High Active 4. Applications To achieve the system performance, consider the power-supply environment and the magneticcoupling situation. The selection of the appropriate power-supply operation mode depends on the quality of supply voltage. If an unregulated supply voltage in the range of = 7 to 16 is available, the internal power supply of the can be used. In this case, standby mode can be used and an external low-current microcontroller can be supplied. If a 5- supply rail is available, it can be used to power the. In this case, please check that the voltage is noise-free. An external power transistor is not necessary. The application depends also on the magnetic-coupling situation. The coupling factor mainly depends on the transmission distance and the antenna coils. The following table lists the appropriate application for a given coupling factor. The magnetic coupling factor can be determined using Atmels test transponder coil. Table 4-1. Magnetic Coupling Magnetic Coupling Factor k > 3% k > 1% k > 0.5% k > 0.3% Appropriate Application Free-running oscillator Diode feedback Diode feedback plus frequency altering Diode feedback plus fine frequency tuning The maximum transmission distance is also influenced by the accuracy of the antenna s resonance. Therefore, the recommendations given above are proposals only. A good compromise for the resonance accuracy of the antenna is a value in the range of f res = 125 khz ±3%. Further details concerning the adequate application and the antenna design is provided in the section Antenna Design Hints. 10

11 The application of the includes the two capacitors C IN and C HP whose values are linearly dependent on the transponder s data rate. The following table gives the appropriate values for the most common data rates. The values are valid for Manchester- and Bi-phase-code. 4.1 Application 1 Table 4-2. Figure 4-1. Application Circuit 1 Recommended Cap alues Data Rate f = 125 khz Input Capacitor (C IN ) Decoupling Capacitor (C HP ) f/32 = 3.9 kbit/s 680 pf 100 nf f/64 = 1.95 kbit/s 1.2 nf 220 nf The following applications are typical examples. The values of C IN and C HP correspond to the transponder s data rate only. The arrangement to fit the magnetic-coupling situation is also independent from other design issues except for one constellation. This constellation, consisting of diode feedback plus fine frequency tuning together with the two-rail power supply, should be used if the transmission distance of is d 10 cm. Application using few external components. This application is for intense magnetic coupling only. 110 kω 5 EXT S Batt 47 nf 47 µf D S DD RF 1N4148 C IN INPUT MS CFE OE STANDBY OUTPUT HIPASS Microcontroller 470 kω 1.5 nf R 1.35 mh COIL1 CH P COIL2 1.2 nf DGND GND SS 11

12 4.2 Application 2 Figure 4-2. Application Circuit 2 Basic application using diode feedback. This application allows higher communication distances than application 1 BC Ω 12 4x 1N kω 22 mf GND 75 kω 4.7 nf 22 µf 22 mf 100 kω 43 kω S EXT D S Batt DD 1.2 nf RF MS COIL 2 CFE 1.35 mh Antenna 82 Ω COIL 1 Standby Microcontroller 1N kω 1.5 nf C IN C HP Input HIPASS DGND Output OE GND I/O SS 12

13 4.3 Application 3 Figure 4-3. Application Circuit 3 This application is comparable to application 2 but alters the operating frequency. This allows higher antenna resonance tolerances and/or higher communication distances. This application is preferred if the detecting microcontroller is close to the as an additional microcontroller signal controls the adequate operating frequency. 4x 1N kω 5 75 kω 4.7 nf 22 µf 47 nf 100 kω 43 kω S EXT D S Batt DD GND 1 nf 1.5 mh Antenna 82 Ω RF COIL 2 COIL 1 MS CFE Standby Microcontroller 1N pf 100 Ω 470 kω 1.5 nf C IN C HP Input HIPASS DGND Output OE GND SS BC kω 1.5 kω Note: Application examples have not been examined for series use or reliability, and no worst case scenarios have been developed. Customers who adapt any of these proposals must carry out their own testing and be convinced that no negative consequences arise from the proposals. 13

14 5. Absolute Maximum Ratings Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. All voltages are referred to GND (Pins 1 and 7) Parameter Pin Symbol Min. Max. Unit Operating voltage 12 Batt S 16 Operating voltage 8, 9, 10, 11, 14 Range of input and output voltages 3, 4, 5, 6, and 13 S, EXT, D S, Coil 1, Coil 2 IN, OUT S Batt Output current 10 I EXT 10 ma Output current 2 I OUT 10 ma Driver output current 8 and 9 I Coil 200 ma Power dissipation SO16 P tot 380 mw Junction temperature T j 150 C Storage temperature T stg C Ambient temperature T amb C 6. Thermal Resistance Parameter Symbol alue Unit Thermal resistance SO16 R thja 120 K/W 7. Operating Range All voltages are referred to GND (Pins 1 and 7) Parameter Symbol alue Unit Operating voltage Pin 12 Batt 7 to 16 Operating voltage Pin 14 S 4.5 to 6.3 Operating voltage Pins 10, 11 EXT, D S 4.5 to 8 Carrier frequency 100 to 150 khz 14

15 8. Electrical Characteristics All voltages are referred to GND (Pins 1 and 7) Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit Data output - Collector emitter - Saturation voltage I out = 5 ma 2 CEsat 400 m Data output enable - Low-level input voltage - High-level input voltage Data input - Clamping level low - Clamping level high - Input resistance - Input sensitivity Driver polarity mode - Low-level input voltage - High-level input voltage Carrier frequency enable - Low-level input voltage - High-level input voltage Operating current f = 3 khz (squarewave) gain capacitor = 100 nf 5- application without load connected to the coil driver 3 il ih il ih R in S IN il ih il ih , 11, 12 and kω m pp I S ma Standby current 12- application 12 I St µa S - Supply voltage - Supply voltage drift - Output current 14 S d s /dt I S m/k ma Driver output voltage - One-rail operation - Battery-voltage operation I L = ±100 ma S, EXT, Batt, D S = 5 Batt = 12 8, 9 DR DR PP PP EXT - Output voltage - Supply voltage drift - Output current - Standby output current Standby input - Low-level input voltage - High-level input voltage Oscillator - Carrier frequency Lowpass filter - Cut-off frequency IC active standby mode Note: 1. REM1: In application 1 where the oscillator operates in free-running mode, the IC must be soldered free from distortion. Otherwise, the oscillator may be out of bounds. 10 EXT d EXT /dt I EXT I EXT il ih m/k ma ma 0.8 RF resistor = 110 kω (application 2), REM 1 (1) f khz Carrier freq. = 125 khz f cut 7 khz Amplifier - Gain C HP = 100 nf 30 15

16 9. Ordering Information Extended Type Number Package Remarks -MFPY SO16 Tube, Pb-free -MFPG3Y SO16 Taped and reeled, Pb-free 10. Package Information Package SO16 Dimensions in mm technical drawings according to DIN specifications Revision History Please note that the following page numbers referred to in this section refer to the specific revision mentioned, not to this document. Revision No. History Put datasheet in a new template Pb-free Logo on page 1 added 4684B-RFID-09/05 New heading rows on Table Absolute Maximum Ratings on page 14 added Ordering Information on page 16 changed 16

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